A ledership check can generate an amount of boon used for characters in the same group. When does this leadership check has to be made? At the players turn as any other skill check? And does the pool of boons carry over to the next rounds?

On Page 71 of the Core Rulebook: there's a list of "Miscellaneous" Significant Actions, which includes:

"Issuing orders to followers."

Since the Leadership skill is the means by which you would do this, a Leadership check would be a Significant Action.

Do the effects carry over to the subsequent round? If the char using Leadership would be the last in the initiative order and the Boons wouldn't carry over the use of the skill would be vain in that case.

Just hope for a better initiative spot in the next round, if you are wanting to give your Leadership a try. Just like in a movie, where the captain is being shelled in a bunker and can't be out there in battle with his troops shouting orders, etc.

He's that one guy without his com-met on, so his crew doesn't know where the stowaway is that shut off their ship's gravatics. He was the last one to wake up, but he knows about the stowaway he let onboard. In the next round, he can pop his head out the door and scream to someone in the hallway, if they are still floating around there.

Depends on what the players are saying where their Travellers are and what they are doing at the moment. If a situation hasn't changed by the time the next round comes, I'll usually apply a Boon on the player again for the same reasons as before. 2D, Boon, and Bane rolls are called on the spot during a Task Check. They are not saved up for later use. If something (say the environment) creates an auto Boon for everyone, I won't ask players for Task Checks. The Travellers get to do all the things.

The boons that result from using leadership in combat, where they can be applied to allies rolls by the player who rolled the leadership check, I think those can carry over, as they are a result of the players check to distribute as they see fit.

There will be limits - they would go away at the end of combat and they can't be allocated to situations outside the leader's knowledge. But round to round in the same fight, Ill let them carry over.

I think they do. There's nothing that says they have to be used in that round.

But it makes sense if they don't carry over. Just because you noticed an opening last round (allowing a Boon to some action) doesn't mean that opening still exists this round, or that someone is in position to exploit that opening.

Personally, I would say they last until right before the Leadership characters next turn. So where he is in the initiative order wouldn't matter.

The boons that result from using leadership in combat, where they can be applied to allies rolls by the player who rolled the leadership check, I think those can carry over, as they are a result of the players check to distribute as they see fit.

There will be limits - they would go away at the end of combat and they can't be allocated to situations outside the leader's knowledge. But round to round in the same fight, Ill let them carry over.

Ok. I forgot about the Leadership player giving out Boons to other players. If time runs out before they can give out all their Boons to players... I suggest players keep doing things. Stay in action. Player characters in contact with the leadership player should have things to do. I've seen players just sit through major and minor actions because they don't participate all that much in their games. I'll have to run some calcs to see what the chances are of more Boons being generated from a Leadership Check than their are total player actions for a round.

ADDED:
I see one issue. That is, the Boons are null and void if the Leadership player is no longer in contact with the player wanting to use their boon they were given.